The present invention relates to a propellant augmented, gas dispensing device, and more particularly to such a device that incorporates apparatus for controlling the release of pressurized gas while allowing rapid depressurization of the propellant chamber to assure extinguishment of unused propellant.
Propellant augmented, gas dispensing devices are utilized for a variety of purposes, including the pressurization of inflatable assemblies, such as escape slides, life rafts, and airbag safety cushions in automobiles. Typical gas dispensing devices of this type have first and second chambers. The first chamber is a storage chamber that carries a relatively inert gas under pressure, for example carbon dioxide, while the second chamber carries a solid propellant, for example ammonimum nitrate. The propellant is utilized as an energy source to heat and pressurize the carbon dioxide gas stored in the first chamber to temperatures on the order of 180.degree. F. and pressures on the order of 5000 psi. Normally, the propellant will pressurize the gas in less than one second. When the gas is pressurized, an outlet burst disc in the exhaust passage from the propellant chamber will rupture, allowing the pressurized gas to pass through the propellant chamber and out the exhaust passage to permit the pressurized gas to do useful work, for example inflate a life raft or other suitable assembly.
These propellant augmented, dispensing devices are designed for operation over ambient temperatures ranging from, for example, -65.degree. F. to 160.degree. F. At lower temperatures, almost all of the solid propellant charge is required to heat the carbon dioxide to 180.degree. F. and pressurize the gas in the storage vessel to approximately 4000 psi. However, when the dispensing device is at a temperature in the intermediate and upper reaches of the operation range, only a portion of the solid propellant is required to pressurize the gas to the desired pressure. Since it is desired that the pressurized gas dispensed from the device is relatively cool, that is, not much hotter than approximately 180.degree. F., it is necessary that the propellant be extinguished immediately after the outlet burst disc ruptures. The propellant is normally extinguished by assuring rapid depressurization of the propellant chamber.
It is, however, sometimes desirable to meter or restrict the flow of pressurized gas from the gas dispensing device in order to dispense the pressurized gas at a relatively low rate. If a restriction is placed in the exhaust channel from the propellant chamber, rapid depressurization of the propellant chamber cannot be achieved and, thus, unused propellant may continue to burn, undesirably raising the temperature of the gas being dispensed by the device.